1. Field of the Invention
The present invention relates generally to a partially plated resin product and a partial plating process there for, more particularly a resin product in which a decorative plating layer is formed only at the required portions on the surface of a resin base material.
2. Description of Related Art
It has generally been proposed to form front grilles of automobiles with resins and to decorate them using plating techniques.
Known techniques are shown for example, in Japanese Examined Patent Publication No. 45-37843 and Japanese Unexamined Patent Publication Nos. 55-152195 and 52-50937. In one of these techniques, as shown in FIG. 18, a contoured groove 72 having a substantially V-shaped cross section is defined on the surface of a base material 71 along the boundary between the to-be-plated or to-be-decorated portion (left side in FIG. 18) and the to-be-unplated portion (right side in FIG. 18). The base material 71 is first subjected to chemical plating to form a chemical plating layer 73 on the entire surface of the base material 71 except for the bottom 72a of the groove 72. Since the bottom 72a of the groove 72 is too narrow to allow a plating solution to intrude thereon, chemical plating cannot substantially be applied to the bottom 72a.
The base material 71 having the chemical plating layer 73 formed thereon is then subjected to an electroplating step, as shown in FIG. 19. The base material 71 is first immersed in a predetermined electroplating solution, and then the chemical plating layer 73 formed on the to-be-plated portion is electrically charged to allow an electroplating layer 74 to be formed thereon. The chemical plating layer 73 formed on the to-be-unplated portion is electrically insulated by the presence of the groove 72, so that the chemical plating layer 73 is dissolved by the electroplating solution and removed from the base material 71. Thus, the chemical plating layer 73 and the electroplating layer 74 can be formed on the base material 71 only at the portions where decorative plating is required.
The above-described technique can be applied when automotive exterior resin equipments such as front grilles and back panels are produced. For example, in the case of front grille, a plating layer is formed on the front surface of a front grille base material at predetermined portions, and a coating layer is formed on the rest of the portions (on the front surface).
In the conventional techniques described above, the plating layer including the chemical plating layer 73 and the electroplating layer 74 is occasionally formed on the front surface of the front grille in insular forms. In this case, the groove 72 is formed on the front surface of the base material 71 so as to form a contour line, and the to-be-plated portions must be electrically charged in the electroplating step. For such purpose, a protrusion serving as an electrode must be formed on the front surface of the base material 71 so as to secure charging. However, when the front grille finally obtained used, the protrusion remains on the front surface thereof which greatly impair the appearance of the product.
The protrusion can be removed after the electroplating step. However, since no plating layer is present at the portion from which the protrusion has been removed, the appearance of the product suffers.